Questions About Survival of Ultraporous Cups in THA
Acetabular components for primary total hip arthroplasty (THA) made with ultraporous surfaces were developed to enhance osseointegration and biological fixation. In the July 1, 2020 issue of The Journal of Bone & Joint Surgery, Palomaki et al. report on a registry study that suggests that implant survival with these components over an average follow-up of 3.6 years is not so “ultra.”
The authors evaluated >6,000 primary THAs that used a Tritanium ultraporous cup and >25,000 THAs that used a conventional cup, all performed between 2009 and 2017. When they compared the two groups for revision for any reason, the 5-year Kaplan-Meier survivorship of the Tritanium group (94.7%) was inferior to that of the conventional-cup group (96.0%). When revision for aseptic loosening was examined, the 5-year survivorship was also inferior for the Tritanium group (99.0%) compared with the conventional group (99.9%). Regression analysis revealed that the Tritanium group had a much higher risk of revision for aseptic loosening 2 to 4 years after surgery (hazard ratio, 11.2; p <0.001). Interestingly, these survivorship and risk-of-revision differences disappeared when the authors analyzed data for the period from May 15, 2014 to December 31, 2017–when the registry was updated to include patient BMI and ASA-class data.
The authors cite several caveats that readers should apply to these findings. The registry did not capture radiographic findings for these patients, so potentially relevant imaging data could not be analyzed. And, despite the database upgrade in 2014, there was a dearth of available data on patient comorbidities. Finally, wide confidence intervals for some of the hazard-ratio calculations suggest the need to confirm revision-risk findings with further research.
Limitations notwithstanding, the study by Palomaki et al. suggests that the performance of ultraporous cups may not meet the hopes and expectations of hip surgeons and their patients.
UKA: Alignment and Overhang Matter
(Reproduced, with permission, from Orthop Traumatol Surg Res. 2016 Apr;102[2]:183-7. Copyright © 2016 Elsevier Masson SAS. All rights reserved.)
These operations were performed by a group of fairly experienced surgeons who averaged >14 UKAs per year, although a commonly used threshold for a “high-volume” UKA surgeon is >15 procedures per year. The cumulative revision rate of 14.2% over 8.7 years, the 5-year Kaplan-Meier survival rate of 88%, and the 10-year survival rate of 70% found by Kazarian et al. are disturbing. Using revision as an endpoint may be problematic because some surgeons are quick to revise a UKA when the radiographic evaluation of component placement is not perfect. Still, this study demonstrates that radiographically determined alignment and overhang “outliers” and “far outliers” had a significantly increased risk of implant failure, compared with patients with good alignment and overhang.
This study did not include UKAs that used computer-assisted methods, but it seems safe to conclude that computer-assisted component placement would be more reliable than “eyeballing,” especially among surgeons with less-experienced eyes. Based on this and other recent studies, I think a controlled trial comparing the functional outcomes and revision rates of UKAs performed with and without computer assistance is warranted.
Marc Swiontkowski, MD
JBJS Editor-in-Chief
Editor’s Note: Click here to read the JBJS Clinical Summary on Unicompartmental Knee Arthroplasty.
Impressive Long-term Outcomes in Revision TKA with Constrained Prostheses
Time is an enemy of all orthopaedic implants, just as it is the bane of native joints. It is therefore helpful to accurately measure how long and well specific implant types last. That is what Kim et al. have done with their 19-year follow up of 90 patients (107 knees) who underwent total knee arthroplasty (TKA) with a constrained condylar knee prosthesis. Their findings appear in the April 15, 2020 issue of The Journal of Bone & Joint Surgery.
Knee arthroplasty surgeons often choose constrained prostheses to improve joint stability in patients with ligament dysfunction, and the typically longer stems of these implants can also compensate for poor bone stock. Kim et al. evaluated the same patient population (mean age of 65 years; mean BMI of 26.9 kg/m2) that they reported on in an earlier study, finding the following outcomes after a mean follow-up of 19 years:
- 96% survival in terms of mechanical failure
- 91% survival in terms of reoperation for any reason
- Patient-reported outcome scores that remained significantly improved from pre-revision values
- Only 1 knee with osteolysis around a component
Among the few knees that required re-revision, 5 such operations were performed due to aseptic loosening and 4 due to infection. The authors note that these very good long-term results are similar to those in previous studies of revision TKAs using various implant types. Kim et al. attribute these findings to several possible factors:
- Low prevalence of comorbidities, including obesity, among the patients
- Excellent surgical technique, including good cementing and correct flexion and extension gaps
- Use of compression-molded polyethylene
Does Computer-Assisted Surgery Drive Better TKA Outcomes?
Computer-assisted surgery (CAS) for total knee arthroplasty (TKA) has become popular largely based on claims that the technology improves accuracy of component positioning and alignment. Theoretically, that leads to superior patient-reported outcomes. However, the use of CSA has not reliably yielded improvements in implant survival or clinical outcomes. A large registry study by Roberts et al. in the April 1, 2020 issue of The Journal sheds additional light on this perplexing question.
An earlier study by the same author group used data from the same New Zealand Joint Registry and showed no difference in functional outcomes or implant survival between TKAs performed with and without CAS.1 However, that study did not account for the potential bias introduced by surgeons who use CAS only for complex cases.
In this study, Roberts et al. analyzed data from 2 carefully selected groups of surgeons: those who used CAS in 90% of their TKAs (“routine CAS” surgeons) and those who used CAS in <10% of their TKAs (“routine conventional” surgeons). Further limiting their analysis to surgeons with >50 TKAs recorded in the registry between 2006 and 2018, Roberts et al. identified 25 “routine CAS” surgeons and 22 “routine conventional” surgeons. This allowed a comparison between 9,501 TKAs performed by routine CAS surgeons and 7,672 TKAs performed by routine conventional surgeons. While analyzing revision rates and Oxford Knee Scores (OKS) at 6 months, 5 years, and 10 years, the authors also controlled for confounding variables such as age, body-mass index, and implant type.
With a mean follow-up of 4.5 years, the authors found a revision rate per 100 component-years of 0.437 in the group operated on by routine CAS surgeons, compared to a mean 4.9-year revision rate of 0.440 in the group operated on by routine conventional surgeons (p=0.724). When stratifying outcomes of patients <65 years old, the authors again found no statistical difference in revision rates. They also found no between-group differences in OKS within the full and <65 cohorts at 6 months, 5 years, or 10 years.
The findings prompt the authors (and I) to wonder whether continually improving design and durability of modern implants make it difficult to discern any advantage from computer assistance in implant positioning.
Matthew R. Schmitz, MD
JBJS Deputy Editor for Social Media
Reference
- Roberts TD, Clatworthy MG, Frampton CM, Young SW. Does computer assisted navigation improve functional outcomes and implant survivability after total knee arthroplasty? J Arthroplasty. 2015 Sep; 30(9)Suppl: 59-63.
THA in the Very Young: Midterm Results
Orthopaedic surgeons work hard to find good alternatives to total hip arthroplasty (THA) in patients <50 years old. That’s because the high functional demands and longer remaining lifespan in these patients can result in excessive wear of the bearing surfaces and loosening of the components—both of which have been documented in multiple publications. But what happens when THA is the most viable solution for a posttraumatic or congenital hip problem in a very young patient because arthrodesis or other osteotomies are not feasible?
In the March 18, 2020 issue of The Journal, Pallante et al. report medium-term outcomes of THA in 78 patients who were ≤20 years of age at the time of surgery, with follow-ups ranging from 2 to 18 years. The findings included the following:
- 10-year survivorship for reoperation of 95.0%
- 10-year survivorship for revision of 97.2%
- 10-year survivorship for complications of 89.5%
Overall, the linear articular wear averaged 0.019 mm/yr in the ceramic-on-ceramic, ceramic-on-highly cross-linked polyethylene, and metal-on-highly cross-linked polyethylene bearings studied, and the average modified Harris hip score in the cohort was 92.
However, despite these impressive clinical and survivorship outcomes, I advise orthopaedists not to lower their resistance to performing THA on these very young patients, many of whom present with hip problems caused by deforming conditions such as Legg-Calve-Perthes disease. We really need 30 to 40 years of outcome data to truly understand what happens with function, revision rates, and wear characteristics in this population. Having said that, I am confident that this group from Mayo will continue reporting on this patient cohort at 5- to 10-year intervals, so that the worldwide orthopaedic community can keep learning from this experience.
Marc Swiontkowski, MD
JBJS Editor-in-Chief
Volume-Outcome Relationships in Reverse TSA
In an OrthoBuzz post from early 2016, JBJS Editor-in-Chief Marc Swiontkowski, MD observed the following about volume-outcome relationships in total hip and total knee arthroplasty: “the higher the surgeon volume, the better the patient outcomes.”
Now, in a national database analysis of >38,200 patients who underwent a reverse total shoulder arthroplasty (RSA), Farley et al. find a similar inverse relationship between hospital volumes of this increasingly popular surgery and clinical outcomes. Reporting in the March 4, 2020 issue of JBJS, they found a similarly inverse relationship between hospital volume and resource utilization.
This study distinguishes itself with its large dataset and by crunching the data into specific hospital-volume strata for each category of clinical outcome (90-day complications, 90-day revisions, and 90-day readmissions) and resource-utilization outcome (cost of care, length of stay, and discharge disposition).
Specifically, on the clinical side, Farley et al. found the following:
- A 1.42 times increased odds of any medical complication in the lowest-volume category (1 to 9 RSAs/yr) compared with the highest-volume category (≥69 RSAs/yr)
- A 1.38 times increased odds of any readmission in the lowest-volume category (1 to 16 RSAs/yr) compared with the highest-volume category (≥70 RSAs/yr)
- A 1.88 times increased odds of any 90-day revision in the lowest-volume category (1 to 16 RSAs/yr) compared with the highest-volume category (≥54 RSAs/yr)
Here are the findings from the resource-utilization side:
- A 4.03 times increased odds of increased cost of care in the lowest-volume category (1 to 5 RSAs/yr) compared with the highest-volume category (≥106 RSAs/yr)
- A 2.26 times increased odds of >2-day length of stay in the lowest-volume category (1 to 10 RSAs/yr) compared with the highest-volume category (≥106 RSAs/yr)
- A 1.68 times increased odds of non-home discharge in the lowest-volume category (1 to 31 RSAs/yr) compared with the highest-volume category (≥106 RSAs/yr)
Farley et al. say hospital volume should be interpreted as a “composite marker” that is probably related to surgical experience, ancillary staff familiarity, and protocolized pathways. They “recommend a target volume of >9 RSAs/yr to avoid the highest risk of detrimental 90-day outcomes,” and they suggest that the outcome disparities could be addressed by “consolidation of care for RSA patients at high-performing institutions.”
More Work, Less Pay for Revision TKAs
Time is a valuable commodity for everyone. Most physicians have spent long hours in the clinic or hospital, away from our families, sometimes missing important life events. We accept those aspects of our chosen profession. But everyone, including surgeons, wants to be appropriately reimbursed for their time. It’s logical that more complex surgical cases take more time to perform correctly and safely. But does Medicare (and the private insurers who base their physician payments on Medicare rates) adequately reimburse for that extra time?
The short answer is “no,” at least in terms of revision surgery for infected total knee arthroplasties (TKAs). Samuel et al. tackle that topic in the February 5, 2020 issue of The Journal. The authors reviewed records from the NSQIP database to identify cases of aseptic revision TKA, 1-stage septic revision TKA, and 2-stage septic revision TKA. Using propensity-score matching that controlled for age, sex, race, BMI, and ASA classification, the authors established 4 cohorts that allowed for comparison of the following types of revision TKA:
- 1-stage, 2-component aseptic revisions (n=1,096)
- 1 stage, 2-component septic revisions (n=274)
- First stage of a 2-stage septic revision (n=274)
- Second stage of a 2-stage septic revision (n=274)
The authors then compared the relative value units (RVUs) for each type of revision TKA. (Medicare uses RVU-based algorithms to reimburse physicians for their services.) The authors also identified operative times for the surgery types and made RVU-per-minute and dollars-per-minute calculations.
The mean operative times were statistically different between each cohort (149 minutes for the aseptic group, 160 minutes for the 1-stage septic group, 138 minutes for the first-stage of the 2-stage septic group, and 170 minutes for the second-stage of the 2-stage septic group). The dollar-per-minute calculation in the “easiest case” of aseptic revision was $7.74 per minute, while in the “hardest case” of a 2-stage septic revision, reimbursement was $5.66 per minute for the first stage and $5.19 per minute for the second stage.
The fact that Medicare’s current reimbursement system does not account for the complexity of treating an infected TKA harms not only surgeons. Financially discouraging physicians from taking complex cases could lead to patients having a difficult time finding a doctor to treat their infected knee replacement. This entire predicament warrants further investigation, possible adjustments to the RVU system, and more realistic valuations of time in the OR.
Matthew R. Schmitz, MD
JBJS Deputy Editor for Social Media
What’s New in Adult Reconstructive Knee Surgery 2020
Every month, JBJS publishes a review of the most pertinent and impactful studies published in the orthopaedic literature during the previous year in 13 subspecialties. Click here for a collection of OrthoBuzz summaries of these “What’s New” articles. This month, author Michael J. Taunton, MD selected the 5 most clinically compelling findings from the more than 130 studies summarized in the January 15, 2020 “What’s New in Adult Reconstructive Knee Surgery.”
Unicompartmental Knee Arthroplasty (UKA)
—A prospective cohort study of 1,000 Oxford cementless UKAs indicated by standard Kozinn and Scott criteria found that revision-free survivorship at 10 years was 97%. Progression of lateral osteoarthritis and dislocation of the bearing were the most common reasons for revision.1
Pain Management
—Authors of a double-blinded, prospective, randomized study assigned 60 primary total knee arthroplasty (TKA) patients to receive either a continuous adductor canal block or a single-injection adductor canal block with adjuvant agents. They found no between-group differences in pain scores up to 42 hours postoperatively.2
Post-TKA Physical Therapy (PT)
—A prospective, randomized, noninferiority trial demonstrated that 290 post-TKA patients who were randomized to either outpatient PT, unsupervised web-based PT at home, or unsupervised printed-instruction-based PT at home had no difference in knee range of motion or in patient-reported outcomes at 4 to 6 weeks or 6 months postoperatively.3
Infection Prevention
—In a retrospective review of 29,695 total joint arthroplasties, preoperative penicillin allergy testing led to a 1.19% higher rate of infection-free survival at 10 years, principally by allowing more routine use of the prophylactic antibiotic cefazolin.4
Revision TKA
—A retrospective case series found that patients undergoing revision TKA at an age of < 50 years had a survivorship free of re-revision of 66% at 10 years. Regardless of the reason for revision, this population also had a higher risk of mortality than the general population at 10 years.5
References
- Campi S, Pandit H, Hooper G, Snell D, Jenkins C, Dodd CAF, et al. Ten-year survival and seven-year functional results of cementless Oxford unicompartmental knee replacement: A prospective consecutive series of our first 1000 cases. Knee. 2018 Dec;25(6):1231-7. Epub 2018/08/29.
- Turner JD, Dobson SW, Henshaw DS, Edwards CJ, Weller RS, Reynolds JW, et al. Single-Injection Adductor Canal Block With Multiple Adjuvants Provides Equivalent Analgesia When Compared With Continuous Adductor Canal Blockade for Primary Total Knee Arthroplasty: A Double-Blinded, Randomized, Controlled, Equivalency Trial. J Arthroplasty. 2018 Oct;33(10):3160-6 e1. Epub 2018/06/16.
- Fleischman AN, Crizer MP, Tarabichi M, Smith S, Rothman RH, Lonner JH, et al. 2018 John N. Insall Award: Recovery of Knee Flexion With Unsupervised Home Exercise Is Not Inferior to Outpatient Physical Therapy After TKA: A Randomized Trial. Clin Orthop Relat Res. 2019 Jan;477(1):60-9. Epub 2019/02/23.
- Wyles CC, Hevesi M, Osmon DR, Park MA, Habermann EB, Lewallen DG, et al. 2019 John Charnley Award: Increased risk of prosthetic joint infection following primary total knee and hip arthroplasty with the use of alternative antibiotics to cefazolin: the value of allergy testing for antibiotic prophylaxis. Bone Joint J. 2019 Jun;101-B(6_Supple_B):9-15. Epub 2019/05/31.
- Chalmers BP, Pallante GD, Sierra RJ, Lewallen DG, Pagnano MW, Trousdale RT. Contemporary Revision Total Knee Arthroplasty in Patients Younger Than 50 Years: 1 in 3 Risk of Re-Revision by 10 Years. J Arthroplasty. 2019 Jul;34(7S):S266-S70. Epub 2019/03/03.
ACL Grafts: Diameter Does Matter, Sort Of
Clinical failure of anterior cruciate ligament (ACL) reconstructions continues to be a too-common scenario. The increasing incidence of ACL revision is due to a variety of factors, including greater intensity of postsurgical physical activity, technical issues, and anatomical influences of the proximal tibia and distal femur. Registries are important sources of data for ACL-related investigations, but I think they are most useful in clarifying experimental designs for more sophisticated clinical research.
In a cohort study in the October 16, 2019 issue of The Journal, Snaebjornsson et al. examined the influence of ACL graft diameter on the risk of revision surgery over 2 years in >18,000 subjects whose data resided in the national knee ligament registries of Sweden and Norway. The vast majority of those patients (92.8%) received a hamstring autograft, with 7.2% receiving a patellar tendon autograft. Overall, the 2-year rate of ACL revision was 2.63% for patellar tendon autografts and 2.08% for hamstring autografts, a statistically nonsignificant difference in relative risk.
However, the authors found an important correlation between graft diameter in the hamstring tendon cohort, with autografts <8 mm in diameter being associated with a higher risk of revision, compared with larger-diameter hamstring autografts. Additionally, patients treated with hamstring graft diameters of ≥9 mm or ≥10 mm had a lower risk of ACL revision surgery than those treated with patellar tendon grafts of any size.
One key limitation that should influence our interpretation of this study is a lack of detail regarding how compliant surgeons were intraoperatively with the use of the measurement device that is depicted in the manuscript and shown above. In addition, the limitations of registry data did not permit the authors to adjust for postsurgical exposures, such as return to sport, the increasing intensity of which makes rerupture more likely. Additional relevant information that would have aided interpretation of the findings includes the relative size of the tibia and femur, lateral condyle size and shape, and proximal tibial slope.
Despite these limitations, this study should prompt further research that uses robust clinical designs to more fully investigate the impact of graft diameter on ACL rerupture rates.
Marc Swiontkowski, MD
JBJS Editor-in-Chief
Let’s Continue Improving Hip-Implant Longevity
In October 2017, JBJS published results from a 10-year randomized controlled trial by Devane et al. documenting the dramatic reduction in polyethylene wear in total hip arthroplasties (THAs) using highly cross-linked polyethylene (HXLPE). This followed decades of research documenting that wear debris was implicated in macrophage activity that was ultimately responsible for implant loosening. In the September 4, 2019 issue of The Journal, Hart and colleagues produce further evidence of the improved performance of HXLPE, this time showing revision rates among THA patients with osteonecrosis that rival the rates among patients with osteoarthritis.
In this matched cohort of 922 THAs performed from 1999 to 2007 that used an HXLPE bearing, the 15-year cumulative rate of revision was 6.6% among patients treated for osteonecrosis and 4.5% among patients treated for osteoarthritis (p = 0.09). There were no radiographic signs of component loosening in the entire cohort, and, despite a lower median preoperative Harris hip score (HHS) among patients with osteonecrosis, both groups had marked improvements in HHS score. These findings are especially noteworthy because patients with osteonecrosis typically undergo THA at an earlier age and have much higher functional demands than the typical 70- or 80-year-old osteoarthritis patient.
However, the 15-year revision rate—even with HXLPE—remains at 4.5% for osteoarthritis patients, which should provide impetus to continue our work identifying all possible factors and mechanisms that lead to THA revision. A partial list would include bearing-surface wear, reliability of implantation, biomechanics, biomaterials, and patient perception of postoperative pain. Also, in a subgroup analysis, Hart et al. found that the 15-year rate of any reoperation among osteonecrosis patients ranged from 0% for hips with radiation-induced osteonecrosis to 25% for hips with idiopathic osteonecrosis. These findings add to the list of factors for THA success that need further investigation.
The work list for improvements in THA will remain substantive for at least the next few decades, and we may never get to 0% revisions for all patients. But we have certainly demonstrated that our research can produce very worthwhile results.
Marc Swiontkowski, MD
JBJS Editor-in-Chief
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